The new user will be created using home_dir as the value for the user’s login directory. The default is to append the login name to default_home and use that as the login directory name.

-e [expire_date]

The date on which the user account will be disabled. The date is specified in the format YYYY-MM-DD.

-f [inactive_time]

The number of days after a password expires until the account is permanently disabled. A value of 0 disables the account as soon as the password has expired, and a value of -1 disables the feature. The default value is -1.

-g [initial_group]

The group name or number of the user’s initial login group. The group name must exist. A group number must refer to an already existing group. The default group number is 1.

-G [group,[,…]]

A list of supplementary groups which the user is also a member of. Each group is separated from the next by a comma, with no intervening whitespace. The groups are subject to the same restrictions as the group given with the -g option. The default is for the user to belong only to the initial group.

-m

The user’s home directory will be created if it does not exist. The files contained in skeleton_dir will be copied to the home directory if the -k option is used, otherwise the files contained in /etc/skel will be used instead. Any directories contained in skeleton_dir or /etc/skel will be created in the user’s home directory as well. The -k option is only valid in conjunction with the -m option. The default is to not create the directory and to not copy any files.

-p [passwd]

The encrypted password, as returned by crypt. The default is to disable the account.

-s

The name of the user’s login shell. The default is to leave this field blank, which causes the system to select the default login shell.

-u [uid]

The numerical value of the user’s ID. This value must be unique, unless the -o option is used. The value must be non-negative. The default is to use the smallest ID value greater than 99 and greater than every other user. Values between 0 and 99 are typically reserved for system accounts.

-b [default_home]

The initial path prefix for a new user’s home directory. The user’s name will be affixed to the end of default_home to create the new directory name if the -d option is not used when creating a new account.

-e [default_expire_date]

The date on which the user account is disabled.

-f [default_inactive]

The number of days after a password has expired before the account will be disabled.

-g [default_group]

The group name or ID for a new user’s initial group. The named group must exist, and a numerical group ID must have an existing entry.

-s [default_shell] -M

The name of the new user’s login shell. The named program will be used for all future new user accounts. Specifies not to create home directory for the user

Eg:

1. # useradd -d /opt/testuser -m testuser

-d Testuser create a home directory under the opt directory

-m To copy the skel directory to the user home directory

# passwd testuser

# ls –la /opt/testuser

To check the command user is created or not

2. # useradd –s /bin/nologin testuser

To add the user but not allow to login using option -s

3. # useradd –e 2012-07-31 testuser

To set expire date of the testuser using option –e

4. # useradd –M testuser

To create a user without home directory using option –M

5. # useradd –D

Its displays below the entries

GROUP: This is the only option which will not be taken as default. Because if you don’t specify -n option a group with same name as the user will be created and the user will be added to that group. To avoid that and to make the user as the member of the default group you need to give the option -n.

HOME: This is the default path prefix for the home directory. Now the home directory will be created as /home/USERNAME.

INACTIVE: -1 by default disables the feature of disabling the account once the user password has expired. To change this behavior you need to give a positive number which means if the password gets expired after the given number of days the user account will be disabled.

EXPIRE: The date on which the user account will be disabled.

SHELL: Users login shell.

SKEL: Contents of the skel directory will be copied to the users home directory.

CREATE_MAIL_SPOOL: According to the value creates or does not create the mail spool.

The -f {days} option set number of days after the password expires until the account is disabled. (If 0 is specified, the account is disabled immediately after the password expires. If -1 is specified, the account is not be disabled after the password expires.)